1. Field of the Invention
The present invention generally relates to semiconductor substrate processing systems. More specifically, the present invention relates to methods and apparatus for performing deposition processes in semiconductor substrate processing systems.
2. Description of the Related Art
In the fabrication of integrated circuits, deposition processes such as chemical vapor deposition (CVD) or plasma enhanced CVD processes are used to deposit films of various materials upon semiconductor substrates. Herein such processes are collectively referred to as CVD processes. During a CVD process, chemical reactions used for depositing a desired material take place in an enclosed process chamber. When the material is deposited on the substrate, residue comprising this material, as well as by-products of the CVD process, accumulates on the internal walls and other components of the process chamber. The residue builds up, as more substrates are processed in the chamber, and leads to generation of particles and other contaminants and, as such, to degradation of the deposited films. Consequently, it is recommended to clean the interior of the CVD chamber on a regular basis.
When chamber cleaning is performed, production of the integrated circuits is temporarily interrupted. As a result, productivity of the CVD process, as measured by substrate throughput, decreases. In order to increase the productivity, it is necessary to facilitate a cleaning process that increases a number of substrates that may be processed before a need in chamber cleaning arises, as well as to decrease the duration of the cleaning process.
Generally, two types of methods are used to clean the CVD chambers. Both methods use a cleaning gas (e.g., fluorine (F) based gas) to remove post-CVD residue from the interior of the chamber and may be performed without opening the chamber, i.e., in situ.
In the first cleaning method, the cleaning gas is energized to a plasma within a remote plasma source that forms and releases into the CVD chamber free radicals and ionic species of the cleaning gas. In the CVD chamber, the radicals and ionic species chemically react with the residue and transform the residue into volatile compounds. The volatile compounds are then evacuated from the chamber. One such method is disclosed in commonly assigned U.S. patent application Ser. No. 10/122,481, filed Apr. 12, 2002, which is incorporated herein by reference.
In the cleaning second method, the cleaning gas is energized to the plasma inside the CVD chamber using a radio-frequency (RF) plasma source and, as such, the free radicals and ionic species of the cleaning gas can attack the residue and internal parts of the chamber both chemically and physically.
In the prior art, the free radicals and ionic species of the cleaning plasma readily recombine within the CVD chamber during a cleaning procedure. Recombination of the free radicals and ionic species results in formation of reactive species that may chemically react with the material (e.g., aluminum (Al), stainless steel, and the like) of components of the CVD chamber, e.g., a gas distribution plate, a susceptor (substrate pedestal), a substrate heater, a protective lining, and the like. During the cleaning process, such chemical reactions, as well as physical bombardment (e.g., an ionic bombardment) of the internal parts, may cause damage to the CVD chamber. Further, in many applications, these chemical reactions can produce non-volatile residue-like deposits (e.g., aluminum fluoride (AlF3)), which also may contaminate the substrates during the following CVD processing of the substrates.
Therefore, there is a need in the art for a method and apparatus for cleaning a CVD chamber with minimal damage to the internal parts.